description
- Oats can claim to be the only 'European' cereal. Previous work indicated that its closest wild relatives are found around Turkey near sites where wheat and barley were first domesticated, but archaeological evidence points to first use as a crop only late in the development of agriculture and then in Central Europe, rather than in its original environment. A plausible explanation for this transfer is that a population of the wild relative (Avena sterilis), which colonises broken ground, had become adapted to life as an agricultural weed. The new weed (A. fatua) is less able to spread in the wild but is very successful at colonising tilled fields of cereals such as barley. A. fatua could have spread across Europe with those crops and then become a crop in its own right in hard times where others failed. Indeed, oats have traditionally been grown on poor ground and at the end of rotations when soil fertility is low, a possible legacy of this secondary domestication. At some stage completely non-shattering oats would have been selected for easier grain harvest and storage, and greater pressure would have been applied for full domestication (loss of awns, larger grain size and so on). A complication for this model is that oats appear to have been domesticated twice. Most cultivars now resemble 'white' oats (A. sativa), sown in the spring and most closely related to wild populations in central Turkey. However, around the Mediterranean, traditional landraces are often 'red' oats (A. byzantina), sown in autumn and most closely related to wild populations in south western Turkey. Modern breeding programmes are largely based on crosses between these two types, and the UK's unique winter oat cultivars may be particularly dependent on A. byzantina traits. We have a strong interest in understanding the origin of both red and white oats, and the role of A. fatua. This is not only driven by curiosity about the development of agriculture but also by the need to add new variation to the modern crop. Each domestication step has created genetic bottlenecks where potentially valuable germplasm has been lost. Better understanding of these bottlenecks, and of natural variation in wild populations, will help find useful variation to incorporate into breeding programmes. Genotyping-by-sequence (GbS) is a recent high throughput method to reveal genetic variation across entire genomes. It samples short sequences adjacent to specific restriction enzyme sites, and does not require prior knowledge of which variants are present. Hundreds of samples may be processed, making it ideal for diversity screens. We have panels of over 500 weedy, wild and landrace accessions already screened by GbS. Unfortunately, the oat genome is almost as large and complex as that of wheat, and no reference is yet available to associate GbS tags with neighbouring genes. Even when the first references become available (expected in 2018), they will have been derived from modern cultivars which may differ from the ancestral stocks we are studying. In this project we will bridge the gap between GbS and genome references to assess gene variation either directly or by improving the references available. In the first step we will use a newly developed sequencing approach to cut the cost of building a red oat reference. In the second we will work with a German barley expert who developed exome capture, a method that samples and sequences only targeted gene regions, and with a Canadian partner who has created an exome capture for oats, based in part on our genome data. We will use an improved design to recover comprehensive collections of gene sequences from 220 key GbS panel accessions. Finally we will obtain sequence from progenitors that will allow comparisons of gene content and order with modern cultivars, and will enhance analysis of exome and GbS data. Working with a Polish partner who has created hybrid populations, we will identify key genes underpinning domestication.